Current Publications
Fluid–structure interaction simulations to investigate the asymmetrical pattern and energy transfer during vocal fold vibrations
GuofengHe, Qilin Liu, Weibing Cai, Azure Wilson, Mohammad Hossein Doranehard, LeaSayce, HaoxiangLuo, and ZhengLi
Asymmetrical vocal fold vibration is the cause of many voice problems. In this study, a two-dimensional fluid–structure interaction model is developed with the finite element method in COMSOL Multiphysics. The vocal folds with asymmetric stiffness are simulated and compared with the symmetric vocal folds as well as unilateral immobile vocal folds. The vocal fold vibration pattern and energy exchange between the fluid and vocal fold structure are analyzed. The results show that the unilateral vocal fold paralysis (UVFP) and the stiffness difference between the two vocal folds would lead to a decrease in the vibration amplitude compared with symmetrical conditions. The asymmetrical vocal fold vibration allows a frequency lock-in between two sides of the vocal fold, and the lock-in frequency is sensitive to the vocal fold stiff ness. The vocal fold vibration can maintain a quasi-periodic pattern when the stiffness difference is less than 5MPa. 10MPa stiffness differ ence can trigger a transition from the quasi-periodic state to the chaotic state. The energy conversion efficiency between fluid and structure is reduced in the presence of a stiffness difference and under UVFP conditions. This efficiency is further decreased when chaotic vibration hap pens, indicating the importance of vibration regularity in maintaining effective fluid-to-structure energy transfer.
Acoustic properties of symmetric and asymmetric vocal fold vibration
Qilin Liu, GuofengHe, LeaSayce, HaoxiangLuo, and ZhengLi
To investigate the acoustic properties of signals generated by symmetric and asymmetric vocal fold vibrations, a flow-acoustic splitting method is employed to model the glottal airflow associated with voice production. The perturbed compressible pressure, p0, is calculated by the linearized perturbed compressible equations (LPCE). Based on p0 and the source term of the LPCE, acoustic behavior related to the medial thickness of the vocal fold and the frequency difference between the two sides of the vocal fold are analyzed. The results show that the opposite-polarity source pair is responsible for the production of p0 and the opposite-polarity source pair is located right at the entrance of the glottal gap. The frequency difference of the two sides diminishes the opposite-polarity source pair and causes amplitude modulation of p0. Consequently, asymmetric vibration can lead to voice problems. The increase in the medial thickness makes the distribution of the paired sources more compact and stronger, and it enhances the intensity ratio between the p0 and the hydrodynamic pressure variation, thereby pos itively contributing to voice production.
An airfoil-based synthetic actuator disk model for wind turbine aerodynamic and structural analysis
Muhammad Rubayat Bin Shahadat, Mohammad Hossein Doranehgard, Weibing Cai,
Charles Meneveau, Benjamin Schafer, Zheng Li
This study introduces an airfoil-based refinement technique to enhance the Actuator Disk Model (ADM) for improved wind turbine aerodynamic load prediction and structural simulation in conjunction with Large Eddy Simulations of the wind flow. While ADM offers higher computational efficiency than the more detailed but resource-intensive Actuator Line Model (ALM), it traditionally lacks the resolution needed to capture the localized blade forces accurately. To address this limitation, we introduce a refinement technique that uses airfoil-specific data and employs interpolation-based grid point refinement, achieving ALM-comparable accuracy while preserving ADM’s efficiency. Unlike conventional ADM that provides only rotor-disk averaged forces, our synthetic method tracks transient aerodynamic load variations over multiple blade revolutions, allowing us to calculate the distributions of maximum and minimum loads during typical cycles. Applied to the NREL 5 MW reference turbine, our enhanced ADM accurately predicts key aerodynamic parameters (angle of attack, axial velocity, lift, drag, axial and tangential forces along the blades) as well as structural responses (blade tip deflection, maximum stress, and stress concentration). Our results show that the tip deflection ranges from 2.33m (3.69 % of blade length) to 4.28m (6.79 %), with maximum stress concentration occurring near the blade root. This research demonstrates that a refined synthetic ADM approach can serve as a computationally efficient alternative for both aerodynamic analysis and structural simulation of wind turbine blades subjected to realistic wind fields.
Large eddy simulation of wind farm performance in horizontally and vertically staggered layouts
Muhammad Rubayat Bin Shahadat, Mohammad Hossein Doranehgard, Weibing Cai, Zheng Li
This numerical investigation employs Large Eddy Simulation (LES) coupled with Actuator Disk Model (ADM) to evaluate wind farm layout optimization strategies. The study presents a systematic analysis of aligned, horizontal staggering, vertical staggering, and mixed (combination of horizontal and vertical) staggering configurations, aiming to establish optimal design parameters for enhanced power production. The investigation examines key performance metrics including mean velocity distributions, turbulence intensity characteristics, and power generation efficiency. Results demonstrate better performance of both horizontal and vertical staggering patterns compared to conventional aligned configurations, with horizontal staggering exhibiting notably higher power output than vertical arrangements. Our findings also suggest that mixed configurations, incorporating both horizontal and vertical staggering, can offer optimal performance characteristics. This research advances the understanding of wake interactions in complex wind farm layouts and provides design guidelines for maximizing wind farm power generation efficiency through strategic turbine positioning.
Comparative analysis of drug deposition patterns among three commercial nasal spray brands: A computational and experimental study
Guiliang Liu, Mohammad Hossein Doranehgard, Xuan Ruan, Bingkai Chen, Brent Senior, Adam Kimple, Rui Ni, Zheng Li
This study investigates drug deposition patterns in nasal drug delivery by combining experimental measurements with computational fluid dynamics simulations. We analyzed three, over the counter, mometasone nasal spray devices, experimentally characterizing particle diameter (dp), spray velocity (up), and spray angle (α). Unlike previous studies that relied on assumed parameters or single-brand analyses, we conducted comparative analyses using measured parameters integrated into COMSOL Multiphysics simulations. The study optimized the Line of Sight (LOS) method by exploring various spray positions and instructions to avoid anterior loss of medication in the anterior nasal cavity. Results revealed that Brand 3, with its narrow spray angle, achieved superior drug delivery efficiency when properly aligned with the target region. However, its performance decreased significantly when misaligned due to its smaller spray cone angle. Our findings show that sprays with narrower cone angles delivered medicine more effectively to the ostiomeatal complex (OMC) with up to 44% higher efficiency using the LOS method. Additionally, in cases with septal deviation, we observed a 14–20% higher drug deposition rate in the right nasal cavity compared to the left. The LOS method significantly improved drug deposition by 2.86–3 times, while the Deep Spray method further enhanced it by 38–50%. This integrated experimental-computational approach provides practical insights for optimizing nasal spray device design and administration techniques, particularly considering anatomical variations.
Computational Modeling of Nasal Cavity Aerodynamics: Implications for Surgical Outcomes and Targeted Drug Administration
Guiliang Liu, W. Jared Martin, Yasine Mirmozaffari, Rui Ni, and Zheng Li
The primary goal of sinonasal surgery is to improve a patient’s quality of life, which is generally achieved by enhancing drug delivery (eg, saline rinses, nasal steroids) and nasal airflow. Both drug delivery and nasal airflow are dependent on the anatomic structure of the sinonasal cavity and the relationship between this anatomy and airflow and drug delivery can be studied using computational fluid dynamics (CFD). CFD generally uses computed tomography scans and computational algorithms to predict airflow or drug delivery and can help us understand surgical outcomes and optimize drug delivery for patients. This study employs CFD to simulate nasal airflow dynamics and optimize drug delivery in the nasal cavity to highlight the utility of CFD for studying sinonasal disease. Utilizing COMSOL Multiphysics software, we developed detailed models to analyze changes in airflow characteristics before and after functional endoscopic sinus surgery, focusing on pressure distribution, velocity profiles, streamline patterns, and heat transfer. This research examines the impact of varying levels of nasal airway obstruction on airflow and heat transfer. In addition, we explore the characteristics of nasal drug delivery by simulating diverse spray parameters, including particle size, spray angle, and velocity. Our comprehensive approach allows for the visualization of drug particle trajectories and deposition patterns, providing crucial insights for enhancing surgical outcomes and improving targeted drug administration. By integrating patient-specific nasal cavity models and considering factors such as airway outlet pressure, this study offers valuable data on pressure cross-sections, flow rate variations, and particle behavior within the nasal passages. The findings of this research can be useful for both surgical planning and the development of more effective nasal drug delivery methods, potentially leading to enhanced clinical outcomes in respiratory treatment.